Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be accessed by various types of access terminals adapted to facilitate wireless communications, where multiple access terminals share the available system resources (e.g., time, frequency, and power).
To enable sharing of the wireless channel by large numbers of transmitting devices, many systems utilize code division multiple access (CDMA), where transmitted data is spread utilizing a suitable pseudo-random number (PN) spreading code, different PN codes being used by each transmitter. To retrieve the data, a receiver despreads the received signal using a correlation receiver. This way, undesired interfering signals, spread with different (ideally, orthogonal) PN spreading codes, have a low correlation and can be discarded by the correlation receiver.
Because conventional matched filter CDMA receivers are inherently interference-limited, various multiuser detection techniques, such as interference cancellation (IC) receivers, have been developed for CDMA receivers to combat such multiple access interference. IC receivers generally create an estimate of the multiple access interference and subtract that estimate from the received signal.
As the demand for mobile broadband access continues to increase, research and development continue to advance the technology not only to meet the growing demand for mobile broadband access, but to advance and enhance the user experience with mobile communications.